Secondhand smoke isn’t as bad as we thought.

Helena, Montana, does not often make global headlines, but in 2003 the small capital city became known for briefly achieving one of the most astounding public health triumphs ever recorded. In June of the previous year, Helena had implemented a comprehensive smoking ban in its workplaces, bars, restaurants, and casinos. In the first six months of the ban, the rate of heart attacks in the city plummeted by nearly 60 percent. Just as remarkably, when a judge struck down the smoking ban in November of that year, the rate of heart attacks shot right back up to its previous level.

For three anti-smoking advocates—local physicians Richard Sargent and Robert Shepard, and activist and researcher Stanton Glantz from the University of California at San Francisco—this sudden drop in heart attacks was proof that smoking bans usher in extraordinary benefits for public health. “This striking finding suggests that protecting people from the toxins in secondhand smoke not only makes life more pleasant; it immediately starts saving lives,” said Glantz in a press release sent out by UCSF.